1. Field of the Invention
The invention relates to a laser telemeter having separate transmitting and receiving optical systems, and at least monocular target observation.
2. Description of the Related Art
The majority of the known laser telemeters are based on the following principle. A collimated laser beam is produced and is directed via a transmitting optical system at a remote target. The laser light reflected by the target is picked up by the receiving optical system and fed to a detector. The receiving optical system is usually also used for target observation. Such a device is disclosed, for example, in German Publication DE 41 35 615 A1. A binocular observation device with a laser telemeter is disclosed in German Publication DE 37 04 848 A1.
Particularly in the case of small targets, it is necessary to collimate the laser beam well. It is desirable for the distance-dependent size of the laser spot to be smaller than the cross-section of the target to be measured, in order both to achieve very high laser light intensity on the target and to selectively influence the transmitted beam by the target to be measured.
The optical parameters of the transmitting optical system determine the divergence of the transmitted beam. The intensity of the laser light arriving at the detector and reflected by the target depends on the optical parameters of the receiving optical system, essentially on its diameter. The optical parameters of the transmitting and receiving optical systems therefore directly influence the maximum range of the laser telemeter.
An increase in the range can be achieved either by increasing the laser power or by making the transmitting and receiving optical systems larger. The maximum laser power is limited on the one hand by regulations relating to safety for the eyes and moreover by the capacity of the energy source for operating the laser. The disadvantages of increasing the dimensions of the optical systems are the associated inconvenience of handling and greater weight.
The technical complexities associated with a larger range have led to the development and optimization of specially designed laser telemeters for different ranges. The users of such devices must therefore decide on different devices depending on the measuring range required and may have to acquire several devices.
The readiness of the devices for use additionally depends on the weather conditions, which may hinder the transmission of the optical radiation. A device designed for relatively long ranges may, under unfavorable circumstances therefore, also be used for shorter distances at which the device designed for these ranges has failed. However, the disadvantage is that only the limited field of view designed for more remote targets is constantly available for the target observation. In case of doubt, the users will nevertheless have to decide in favor of the technically more complex, and therefore more expensive, device.